#DD0032

CSS

:root {
  --rare-red: #dd0032;
  --rare-red-rgb: 221 0 50;
  --rare-red-oklch: oklch(0.567 0.228 21.9);
}

.element {
  color: var(--rare-red);
  background-color: hsl(346 100% 43%);
  border-color: oklch(0.567 0.228 21.9);
}

Tailwind CSS v4

@theme {
  --color-rare-red: #dd0032;
  --color-rare-red-50: #ffdcd6;
  --color-rare-red-100: #ffcac3;
  --color-rare-red-200: #ffaba4;
  --color-rare-red-300: #ff817d;
  --color-rare-red-400: #ff545e;
  --color-rare-red-500: #f90039;
  --color-rare-red-600: #d30d31;
  --color-rare-red-700: #aa0e27;
  --color-rare-red-800: #7f061f;
  --color-rare-red-900: #5a0514;
  --color-rare-red-950: #3c0006;
}

SCSS

$rare-red: #dd0032;
$rare-red-rgb: 221, 0, 50;
$rare-red-light: mix(#fff, $rare-red, 20%);
$rare-red-dark: mix(#000, $rare-red, 20%);

.element {
  color: $rare-red;
  box-shadow: 0 0 0 2px rgba($rare-red, 0.35);
}